Oxidant/catalyst nanoparticles to reduce tobacco smoke constituents such as carbon monoxide

ABSTRACT

Cut filler compositions, cigarettes, methods for making cigarettes and methods for smoking cigarettes are provided, which involve the use of nanoparticle additives capable of reducing amounts of at least one constituent from mainstream and/or sidestream tobacco smoke, the at least one constituent being selected from the group consisting of aldehyde, carbon monoxide, 1,3-butadiene, isoprene, acrolein, acrylonitrile, hydrogen cyanide, o-toluidine, 2-naphtylamine, nitrogen oxide, benzene, N-nitrosonornicotine, phenol, catechol, benz(a)anthracene, benzo(a)pyrene, and mixtures thereof. Preferably, the nanoparticle additives are effective as an oxidant for the conversion of carbon monoxide to carbon dioxide and/or as a catalyst for the conversion of carbon monoxide to carbon dioxide and/or catalyst for conversion of aldehydes such as acetaldehyde and acrolein, hydrocarbons such as isoprene and/or phenolic compounds such as catechol to carbon dioxide and water vapor.

This application is a continuation-in-part of application Ser. No.10/286,968, filed Nov. 4, 2002 which is a continuation-in-part ofapplication Ser. No. 09/942,881, filed Aug. 31, 2001.

FIELD OF INVENTION

The invention relates generally to methods for reducing constituentssuch as carbon monoxide in the mainstream smoke of a cigarette duringsmoking. More specifically, the invention relates to cut fillercompositions, cigarettes, methods for making cigarettes and methods forsmoking cigarettes, which involve the use of nanoparticle additivescapable of reducing the amounts of various constituents in tobaccosmoke.

BACKGROUND

Various methods for reducing the amount of carbon monoxide in themainstream smoke of a cigarette during smoking have been proposed. Forexample, British Patent No. 863,287 describes methods for treatingtobacco prior to the manufacture of tobacco articles, such thatincomplete combustion products are removed or modified during smoking ofthe tobacco article. This is said to be accomplished by adding a calciumoxide or a calcium oxide precursor to the tobacco. Iron oxide is alsomentioned as an additive to the tobacco.

Cigarettes comprising absorbents, generally in a filter tip, have beensuggested for physically absorbing some of the carbon monoxide, but suchmethods are usually not completely efficient. A cigarette filter forremoving unwanted byproducts formed during smoking is described in U.S.Reissue Patent No. RE 31,700, where the cigarette filter comprises dryand active green algae, optionally with an inorganic porous adsorbentsuch as iron oxide. Other filtering materials and filters for removingunwanted gaseous byproducts, such as hydrogen cyanide and hydrogensulfide, are described in British Patent No. 973,854. These filteringmaterials and filters contain absorbent granules of a gas-adsorbentmaterial, impregnated with finely divided oxides of both iron and zinc.In another example, an additive for smoking tobacco products and theirfilter elements, which comprises an intimate mixture of at least twohighly dispersed metal oxides or metal oxyhydrates, is described in U.S.Pat. No. 4,193,412. Such an additive is said to have a synergisticallyincreased absorption capacity for toxic substances in the tobacco smoke.British Patent No. 685,822 describes a filtering agent that is said tooxidize carbon monoxide in tobacco smoke to carbonic acid gas. Thisfiltering agent contains, for example, manganese dioxide and cupricoxide, and slaked lime. The addition of ferric oxide in small amounts issaid to improve the efficiency of the product.

The addition of an oxidizing reagent or catalyst to the filter has beendescribed as a strategy for reducing the concentration of carbonmonoxide reaching the smoker. The disadvantages of such an approach,using a conventional catalyst, include the large quantities of oxidantthat often need to be incorporated into the filter to achieveconsiderable reduction of carbon monoxide. Moreover, if theineffectiveness of the heterogeneous reaction is taken into account, theamount of the oxidant required would be even larger. For example, U.S.Pat. No. 4,317,460 describes supported catalysts for use in smokingproduct filters for the low temperature oxidation of carbon monoxide tocarbon dioxide. Such catalysts include mixtures of tin or tin compounds,for example, with other catalytic materials, on a microporous support.Another filter for smoking articles is described in Swiss patent609,217, where the filter contains tetrapyrrole pigment containing acomplexed iron (e.g. haemoglobin or chlorocruorin), and optionally ametal or a metal salt or oxide capable of fixing carbon monoxide orconverting it to carbon dioxide. In another example, British Patent No.1,104,993 relates to a tobacco smoke filter made from sorbent granulesand thermoplastic resin. While activated carbon is the preferredmaterial for the sorbent granules, it is said that metal oxides, such asiron oxide, may be used instead of, or in addition to the activatedcarbon. However, such catalysts suffer drawbacks because under normalconditions for smoking, catalysts are rapidly deactivated, for example,by various byproducts formed during smoking and/or by the heat. Inaddition, as a result of such localized catalytic activity, such filtersoften heat up during smoking to unacceptable temperatures.

Catalysts for the conversion of carbon monoxide to carbon dioxide aredescribed, for example, in U.S. Pat. Nos. 4,956,330 and 5,258,330. Acatalyst composition for the oxidation reaction of carbon monoxide andoxygen to carbon dioxide is described, for example, in U.S. Pat. No.4,956,330. In addition, U.S. Pat. No. 5,050,621 describes a smokingarticle having a catalytic unit containing material for the oxidation ofcarbon monoxide to carbon dioxide. The catalyst material may be copperoxide and/or manganese dioxide. The method of making the catalyst isdescribed in British Patent No. 1,315,374. Finally, U.S. Pat. No.5,258,340 describes a mixed transition metal oxide catalyst for theoxidation of carbon monoxide to carbon dioxide. This catalyst is said tobe useful for incorporation into smoking articles.

Metal oxides, such as iron oxide have also been incorporated intocigarettes for various purposes. For example, in WO 87/06104, theaddition of small quantities of zinc oxide or ferric oxide to tobacco isdescribed, for the purposes of reducing or eliminating the production ofcertain unwanted byproducts, such as nitrogen-carbon compounds, as wellas removing the stale “after taste” associated with cigarettes. The ironoxide is provided in particulate form, such that under combustionconditions, the ferric oxide or zinc oxide present in minute quantitiesin particulate form is reduced to iron. The iron is claimed todissociate water vapor into hydrogen and oxygen, and cause thepreferential combustion of nitrogen with hydrogen, rather than withoxygen and carbon, thereby preferentially forming ammonia rather thanthe unwanted nitrogen-carbon compounds.

In another example, U.S. Pat. No. 3,807,416 describes a smoking materialcomprising reconstituted tobacco and zinc oxide powder. Further, U.S.Pat. No. 3,720,214 relates to a smoking article composition comprisingtobacco and a catalytic agent consisting essentially of finely dividedzinc oxide. This composition is described as causing a decrease in theamount of polycyclic aromatic compounds during smoking. Another approachto reducing the concentration of carbon monoxide is described in WO00/40104, which describes combining tobacco with loess and optionallyiron oxide compounds as additives. The oxide compounds of theconstituents in loess, as well as the iron oxide additives are said toreduce the concentration of carbon monoxide.

Moreover, iron oxide has also been proposed for incorporation intotobacco articles, for a variety of other purposes. For example, ironoxide has been described as particulate inorganic filler (e.g. U.S. Pat.Nos. 4,197,861; 4,195,645; and 3,931,824), as a coloring agent (e.g.U.S. Pat. No. 4,119,104) and in powder form as a burn regulator (e.g.U.S. Pat. No. 4,109,663). In addition, several patents describe treatingfiller materials with powdered iron oxide to improve taste, color and/orappearance (e.g. U.S. Pat. Nos. 6,095,152; 5,598,868; 5,129,408;5,105,836 and 5,101,839). However, the prior attempts to make cigarettesincorporating metal oxides, such as FeO or Fe₂O₃ have not led to theeffective reduction of carbon monoxide in mainstream smoke.

Despite the developments to date, there remains a need for improved andmore efficient methods and compositions for reducing the amount ofcarbon monoxide in the mainstream smoke of a cigarette during smoking.Preferably, such methods and compositions should not involve expensiveor time consuming manufacturing and/or processing steps. Morepreferably, it should be possible to catalyze or oxidize carbon monoxidenot only in the filter region of the cigarette, but also along theentire length of the cigarette during smoking.

SUMMARY

The invention provides cut filler compositions, cigarettes, methods formaking cigarettes and methods for smoking cigarettes which involve theuse of nanoparticle additives capable of reducing the amounts of variousconstituents in tobacco smoke

In a preferred embodiment, the additive is capable of reducing at leastone constituent from mainstream and/or sidestream tobacco smoke, the atleast one constituent being selected from the group consisting ofaldehyde, carbon monoxide, 1,3-butadiene, isoprene, acrolein,acrylonitrile, hydrogen cyanide, o-toluidine, 2-naphtylamine, nitrogenoxide, benzene, N-nitrosonornicotine, phenol, catechol,benz(a)anthracene, benzo(a)pyrene, and mixtures thereof. Preferably, theadditive is effective for the conversion of carbon monoxide to carbondioxide and/or catalyst for the conversion of hydrocarbon such asisoprene and/or aldehydes such as acetaldehyde and acrolein and/orphenolic compounds such as catechol to carbon dioxide and water.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the temperature dependence of the Gibbs Free Energy andEnthalpy for the oxidation reaction of carbon monoxide to carbondioxide.

FIG. 2 depicts the temperature dependence of the percentage conversionof carbon dioxide to carbon monoxide by carbon to form carbon monoxide.

FIG. 3 depicts a comparison between the catalytic activity of Fe₂O₃nanoparticles (NANOCAT® Superfine Iron Oxide (SFIO) from MACH I, Inc.,King of Prussia, PA) having an average particle size of about 3 nm,versus Fe₂O₃ powder (from Aldrich Chemical Company) having an averageparticle size of about 5μm.

FIGS. 4A and 4B depict the pyrolysis region (where the Fe₂O₃nanoparticles act as a catalyst) and the combustion zone (where theFe₂O₃ nanoparticles act as an oxidant) in a cigarette.

FIG. 5 depicts a schematic of a quartz flow tube reactor.

FIG. 6 illustrates the temperature dependence on the production ofcarbon monoxide, carbon dioxide and oxygen, when using Fe₂O₃nanoparticles as the catalyst for the oxidation of carbon monoxide withoxygen to produce carbon dioxide.

FIG. 7 illustrates the relative production of carbon monoxide, carbondioxide and oxygen, when using Fe₂O₃ nanoparticles as an oxidant for thereaction of Fe₂O₃ with carbon monoxide to produce carbon dioxide andFeO.

FIGS. 8A and 8B illustrate the reaction orders of carbon monoxide andcarbon dioxide with Fe₂O₃ as a catalyst.

FIG. 9 depicts the measurement of the activation energy and thepre-exponential factor for the reaction of carbon monoxide with oxygento produce carbon dioxide, using Fe₂O₃ nanoparticles as a catalyst forthe reaction.

FIG. 10 depicts the temperature dependence for the conversion rate ofcarbon monoxide, for flow rates of 300 mL/min and 900 mL/minrespectively.

FIG. 11 depicts contamination and deactivation studies for water whereincurve 1 represents the condition for 3% H₂O and curve 2 represents thecondition for no H₂O.

FIG. 12 depicts the temperature dependence for the conversion rates ofCuO and Fe₂O₃ nanoparticles as catalysts for the oxidation of carbonmonoxide with oxygen to produce carbon dioxide.

FIG. 13 depicts a flow tube reactor to simulate a cigarette inevaluating different nanoparticle catalysts.

FIG. 14 depicts the relative amounts of carbon monoxide and carbondioxide production without a catalyst present.

FIG. 15 depicts the relative amounts of carbon monoxide and carbondioxide production with a catalyst present.

FIG. 16 shows the effect of oxidation of carbon monoxide withoutisoprene in the gas stream.

FIG. 17 shows the oxidation of isoprene without the presence of carbonmonoxide in the gas stream.

FIG. 18 shows the effect of simultaneous oxidation of carbon monoxideand isoprene.

FIG. 19 is a proposed model of a cyclopentadienyl-like structure on theiron oxide surface of the catalyst material.

FIG. 20 shows the product distribution for conversion of catechol at350° C. with a 1:1 weight % ratio of substrate to catalyst using 2 mgcatechol and 2.5 mg NANOCAT® catalyst.

FIG. 21 shows the product distribution for conversion of catechol at600° C. in the absence of a catalyst using 2 mg catechol.

FIG. 22 shows the product distribution for conversion of catechol at350° C. with a 10:1 weight % ratio of substrate to catalyst using 20 mgcatechol and 2.5 mg NANOCAT® catalyst.

FIG. 23 shows the product distribution for conversion of catechol at650° C. with a 10:1 weight % ratio of substrate to catalyst using 20 mgcatechol and 2.5 mg NANOCAT® catalyst.

DETAILED DESCRIPTION

The invention provides cut filler compositions, cigarettes, methods formaking cigarettes and methods for smoking cigarettes which involve theuse of nanoparticle additives capable of acting as an oxidant for theconversion of carbon monoxide to carbon dioxide and/or as a catalyst forthe conversion of carbon monoxide to carbon dioxide. Through theinvention, the amount of carbon monoxide in mainstream smoke can bereduced, thereby also reducing the amount of carbon monoxide reachingthe smoker and/or given off as second-hand or sidestream smoke.

The term “mainstream” smoke refers to the mixture of gases passing downthe tobacco rod and issuing through the filter end, i.e. the amount ofsmoke issuing or drawn from the mouth end of a cigarette during smokingof the cigarette. The mainstream smoke contains smoke that is drawn inthrough both the lighted region, as well as through the cigarette paperwrapper.

The total amount of carbon monoxide formed during smoking comes from acombination of three main sources: thermal decomposition (about 30%),combustion (about 36%) and reduction of carbon dioxide with carbonizedtobacco (at least 23%). Formation of carbon monoxide from thermaldecomposition starts at a temperature of about 180° C., and finishes ataround 1050° C., and is largely controlled by chemical kinetics.Formation of carbon monoxide and carbon dioxide during combustion iscontrolled largely by the diffusion of oxygen to the surface (k_(a)) andthe surface reaction (k_(b)). At 250° C., k_(a) and k_(b), are about thesame. At 400° C., the reaction becomes diffusion controlled. Finally,the reduction of carbon dioxide with carbonized tobacco or charcoaloccurs at temperatures around 390° C. and above. Besides the tobaccoconstituents, the temperature and the oxygen concentration are the twomost significant factors affecting the formation and reaction of carbonmonoxide and carbon dioxide.

While not wishing to be bound by theory, it is believed that thenanoparticle additives can target the various reactions that occur indifferent regions of the cigarette during smoking. During smoking thereare three distinct regions in a cigarette: the combustion zone, thepyrolysis/distillation zone, and the condensation/filtration zone.First, the “combustion region” is the burning zone of the cigaretteproduced during smoking of the cigarette, usually at the lighted end ofa cigarette. The temperature in the combustion zone ranges from about700° C. to about 950° C., and the heating rate can go as high as 500°C./second. The concentration of oxygen is low in this region, since itis being consumed in the combustion of tobacco to produce carbonmonoxide, carbon dioxide, water vapor, and various organics. Thisreaction is highly exothermic and the heat generated here is carried bygas to the pyrolysis/distillation zone. The low oxygen concentrationscoupled with the high temperature leads to the reduction of carbondioxide to carbon monoxide by the carbonized tobacco. In this region,the nanoparticle additive acts as an oxidant to convert carbon monoxideto carbon dioxide. As an oxidant, the nanoparticle additive oxidizescarbon monoxide in the absence of oxygen. The oxidation reaction beginsat around 150° C., and reaches maximum activity at temperatures higherthan about 460° C.

The “pyrolysis region” is the region behind the combustion region, wherethe temperatures range from about 200° C. to about 600° C. This is wheremost of the carbon monoxide is produced. The major reaction in thisregion is the pyrolysis (i.e. the thermal degradation) of the tobaccothat produces carbon monoxide, carbon dioxide, smoke components, andcharcoal using the heat generated in the combustion zone. There is someoxygen present in this zone, and thus the nanoparticle additive may actas a catalyst for the oxidation of carbon monoxide to carbon dioxide. Asa catalyst, the nanoparticle additive catalyzes the oxidation of carbonmonoxide by oxygen to produce carbon dioxide. The catalytic reactionbegins at 150° C. and reaches maximum activity around 300° C. Thenanoparticle additive preferably retains its oxidant capability after ithas been used as a catalyst, so that it can also function as an oxidantin the combustion region as well.

Third, there is the condensation/filtration zone, where the temperatureranges from ambient to about 150° C. The major process is thecondensation/filtration of the smoke components. Some amount of carbonmonoxide and carbon dioxide diffuse out of the cigarette and some oxygendiffuses into the cigarette. However, in general, the oxygen level doesnot recover to the atmospheric level.

As mentioned above, the nanoparticle additives may function as anoxidant and/or as a catalyst, depending upon the reaction conditions. Ina preferred embodiment of the invention, the additive is capable ofacting as both an oxidant for the conversion of carbon monoxide tocarbon dioxide and as a catalyst for the conversion of carbon monoxideto carbon dioxide. In such an embodiment, the catalyst will provide thegreatest effect. It is also possible to use combinations of additives toobtain this effect.

By “nanoparticles” is meant that the particles have an average particlesize of less than a micron. The additive preferably has an averageparticle size less than about 500 nm, more preferably less than about100 nm, even more preferably less than about 50 nm, and most preferablyless than about 5 nm. Preferably, the additive has a surface area fromabout 20 m²/g to about 400 m²/g, or more preferably from about 200 m²/gto about 300 m²/g.

The nanoparticles may be made using any suitable technique, or thenanoparticles can be purchased from a commercial supplier. For instance,MACH I, Inc., King of Prussia, PA sells Fe₂O₃ nanoparticles under thetrade names NANOCAT® Superfine Iron Oxide (SFIO) and NANOCAT® MagneticIron Oxide. The NANOCAT® Superfine Iron Oxide (SFIO) is amorphous ferricoxide in the form of a free flowing powder, with a particle size ofabout 3 nm, a specific surface area of about 250 m²/g, and a bulkdensity of about 0.05 g/mL. The NANOCAT® Superfine Iron Oxide (SFIO) issynthesized by a vapor-phase process, which renders it free ofimpurities that may be present in conventional catalysts, and issuitable for use in food, drugs, and cosmetics. The NANOCAT® MagneticIron Oxide is a free flowing powder with a particle size of about 25 nmand a surface area of about 40 m²/g.

Preferably, the selection of an appropriate nanoparticle catalyst and/oroxidant will take into account such factors as stability andpreservation of activity during storage conditions, low cost andabundance of supply. Preferably, the nanoparticle additive will be abenign material. Further, it is preferred that the nanoparticles do notreact or form unwanted byproducts during smoking.

In selecting a nanoparticle additive, various thermodynamicconsiderations may be taken into account, to ensure that oxidationand/or catalysis will occur efficiently, as will be apparent to theskilled artisan. For example, FIG. 1 shows a thermodynamic analysis ofthe Gibbs Free Energy and Enthalpy temperature dependence for theoxidation of carbon monoxide to carbon dioxide. FIG. 2 shows thetemperature dependence of the percentage of carbon dioxide conversionwith carbon to form carbon monoxide.

In a preferred embodiment, metal oxide nanoparticles are used. Anysuitable metal oxide in the form of nanoparticles may be used.Optionally, one or more metal oxides may also be used as mixtures or incombination, where the metal oxides may be different chemical entitiesor different forms of the same metal oxide.

Preferred nanoparticle additives include metal oxides, such as Fe₂O₃,CuO, CeO₂, Ce₂O₃, or doped metal oxides such as Y₂O₃ doped withzirconium, Mn₂O₃ doped with palladium. Mixtures of additives may also beused. In particular, Fe₂O₃ is preferred because it is not known toproduce any unwanted byproducts, and will simply be reduced to FeO or Feafter the reaction. Further, when Fe₂O₃ is used as the additive, it willnot be converted to an environmentally hazardous material. Moreover, useof a precious metal can be avoided, as the Fe₂O₃ nanoparticles areeconomical and readily available. In particular, NANOCAT® Superfine IronOxide (SFIO) and NANOCAT® Magnetic Iron Oxide, described above, arepreferred additives.

FIG. 3 shows a comparison between the catalytic activity of Fe₂O₃nanoparticles (NANOCAT® Superfine Iron Oxide (SFIO) from MACH I, Inc.,King of Prussia, PA) having an average particle size of about 3 nm(curve A), versus Fe₂O₃ powder (from Aldrich Chemical Company) having anaverage particle size of about 5 μm (curve B). The test conditionsinclude flow rate of 1000 ml/min of He containing 20.6% O₂ and 3.4% Co,50 mg catalyst and 12K/min heating rate. The Fe2O₃ nanoparticles show amuch higher percentage of conversion of carbon monoxide to carbondioxide than the Fe₂O₃ having an average particle size of about 5μm.

Fe2O₃ nanoparticles are capable of acting as both an oxidant for theconversion of carbon monoxide to carbon dioxide and as a catalyst forthe conversion of carbon monoxide to carbon dioxide. As shownschematically in FIG. 4A, the Fe₂O₃ nanoparticles act as a catalyst inthe pyrolysis zone A wherein 2CO+O₂→2CO₂, and act as an oxidant in thecombustion region B wherein Fe₂O₃+CO→CO₂+2FeO FIG. 4B shows varioustemperature zones in a lit cigarette wherein zone A representsapproximately 700 to 900° C., zone B represents approximately 200 to600° C. and zone C represents approximately 30 to 200° C. Theoxidant/catalyst dual function and the reaction temperature range makeFe₂O₃ nanoparticles a useful additive in cigarettes and tobacco mixturesfor the reduction of carbon monoxide during smoking. Also, during thesmoking of the cigarette, the Fe₂O₃ nanoparticles may be used initiallyas a catalyst (i.e. in the pyrolysis zone), and then as an oxidant (i.e.in the combustion region).

Various experiments to further study thermodynamic and kinetics ofvarious catalysts were conducted using a quartz flow tube reactor. Thekinetics equation governing these reactions is as follows:ln(1−x)=−A _(o) e ^(−(Ea/RT))•(s•l/F)where the variables are defined as follows:

x=the percentage of carbon monoxide converted to carbon dioxide

A_(o)=the pre-exponential factor, 5×10⁻⁶ s−1

R=the gas constant, 1.987×10⁻³ kcal/(mol•K)

E_(a)=activation energy, 14.5 kcal/mol

s=cross section of the flow tube, 0.622 cm²

l=length of the catalyst, 1.5cm

F=flow rate, in cm³/s

T=temperature

A schematic of a quartz flow tube reactor, suitable for carrying outsuch studies, is shown in FIG. 5. Helium, oxygen/helium and/or carbonmonoxide/helium mixtures may be introduced at one end of the reactor. Aquartz wool 10 dusted with Fe₂O₃ nanoparticles is placed within thereactor between sections of quartz wool 12. The products exit thereactor at a second end, which comprises an exhaust 14 and a capillaryline 16 to a Quadrupole Mass Spectrometer (“QMS”) 18. The relativeamounts of products can thus be determined for a variety of reactionconditions.

FIG. 6 is a graph of temperature versus QMS intensity for a test whereinFe₂O₃ nanoparticles are used as a catalyst for the reaction of carbonmonoxide with oxygen to produce carbon dioxide. In the test, about 82 mgof Fe₂O₃ nanoparticles are loaded in the quartz flow tube reactor.Carbon monoxide is provided at 4% concentration in helium at a flow rateof about 270 mL/min, and oxygen is provided at 21% concentration inhelium at a flow rate of about 270 mL/min. The heating rate is about12.1 K/min. As shown in this graph wherein curve A represents CO, curveB represents O₂ and curve C represents CO₂, Fe₂O₃ nanoparticles areeffective at converting carbon monoxide to carbon dioxide attemperatures above around 225° C.

FIG. 7 is a graph of time versus QMS intensity for a test wherein Fe₂O₃nanoparticles are studied as an oxidant for the reaction of Fe₂O₃ withcarbon monoxide to produce carbon dioxide and FeO. In FIG. 7, curve Arepresents CO, curve B represents O₂ and curve C represents CO₂. In thetest, about 82 mg of Fe₂O₃ nanoparticles are loaded in the quartz flowtube reactor. Carbon monoxide is provided at 4% concentration in heliumat a flow rate of about 270 mL/min, and the heating rate is about 137K/min to a maximum temperature of 460°C. As suggested by data shown inFIGS. 6 and 7, Fe2O₃ nanoparticles are effective in conversion of carbonmonoxide to carbon dioxide under conditions similar to those duringsmoking of a cigarette.

FIGS. 8A and 8B are graphs showing the reaction orders of carbonmonoxide and carbon dioxide with Fe₂O₃ as a catalyst wherein T=218° C.,flow rate=400 ml/min, catalyst=50 mg Fe₂O₃ and O₂ is provided at 11%concentration in FIG. 8A and T=255° C., flow rate=500 ml/min,catalyst=50 mg Fe₂O₃ and CO is provided at 0.79% concentration. FIG. 9depicts the measurement of the activation energy and the pre-exponentialfactor for the reaction of carbon monoxide with oxygen to produce carbondioxide, using Fe₂O₃ nanoparticles as a catalyst for the reaction with4% CO in He at 100 ml/min and 2% O₂ in He at 200 ml/min. A summary ofactivation energies is provided in Table 1. TABLE 1 Summary of theActivation Energies and Pre-exponential Factors Flow Rate A_(o) E_(a)(mL/min) CO % O₂ % (s⁻¹) (kcal/mol) 1 300 1.32 1.34 1.8 × 10⁷ 14.9 2 9001.32 1.34 8.2 × 10⁶ 14.7 3 1000  3.43 20.6 2.3 × 10⁶ 13.5 4 500 3.4320.6 6.6 × 10⁶ 14.3 5 250 3.42 20.6 2.2 × 10⁷ 15.3 AVG.   5 × 10⁶ 14.5Ref. 1 Gas Phase 39.7 2 2% Au/TiO₂ 7.6 3 2.2% 9.6 Pd/Al₂O₃

FIG. 10 depicts the temperature dependence for the conversion rate ofcarbon monoxide using 50 mg Fe₂O₃ nanoparticles as catalyst in thequartz tube reactor with He containing 1.32% CO and 1.34% O₂ flowingthrough the reactor, for flow rates of 300 mL/min (curve A) and 900mL/min (curve B) respectively.

FIG. 11 depicts contamination and deactivation studies for water using50 mg Fe₂O₃ nanoparticles as catalyst in the quartz tube reactor withflow rate of 1000 ml/min He containing 3.4% CO and 21% O₂ and heatingrate of 12.4 K/min. As can be seen from the graph, compared to curve 1(without water), the presence of up to 3% water (curve 2) has littleeffect on the ability of Fe₂O₃ nanoparticles to convert carbon monoxideto carbon dioxide.

FIG. 12 illustrates a comparison between the temperature dependence ofconversion rate for CuO (Curve A) and Fe₂O₃ (Curve B) nanoparticlesusing 50 mg Fe₂O₃ and 50 mg CuO nanoparticles as catalyst in the quartztube reactor with flow rate of 1000 ml/min He containing 3.4% CO and 21%O₂ and heating rate of 12.4 K/min. Although the CuO nanoparticles havehigher conversion rates at lower temperatures, at higher temperaturesthe CuO and Fe₂O₃ have the same conversion rates.

FIG. 13 shows a flow tube reactor to simulate a cigarette in evaluatingdifferent nanoparticle catalysts wherein the reactor 20 includes aninlet 22 for 21% O₂ in He, ⅛ inch stainless steel tubing 24, tobaccofiller 26, Fe₂O₃ or other oxides dusted on quartz wool 28, vent 30 andQMS analyzer 32. Table 2 shows a comparison between the ratio of carbonmonoxide to carbon dioxide, and the percentage of oxygen depletion whenusing CuO and Fe₂O₃ nanoparticles. TABLE 2 Comparison between CuO andFe₂O₃ nanoparticles Nanoparticle CO/CO₂ O₂ Depletion (%) None 0.51 48CuO 0.29 67 Fe₂O₃ 0.23 100

In the absence of nanoparticles, the ratio of carbon monoxide to carbondioxide is about 0.51 and the oxygen depletion is about 48%. The data inTable 2 illustrates the improvement obtained by using nanoparticles. Theratio of carbon monoxide to carbon dioxide drops to 0.29 and 0.23 forCuO and Fe₂O₃ nanoparticles, respectively. The oxygen depletionincreases to 67% and 100% for CuO and Fe₂O₃ nanoparticles, respectively.

FIG. 14 is a graph of temperature versus QMS intensity in a test whichshows the amounts of carbon monoxide (curve A) and carbon dioxide (curveB) production without a catalyst present using 1000 ml/min He containing21% 02, 350 mg tobacco and heating rate of 120 K/min. FIG. 15 is a graphof temperature versus QMS intensity in a test which shows the amounts ofcarbon monoxide and carbon dioxide production when using 50 mg Fe₂O₃nanoparticles as a catalyst with 1000 ml/min He containing 21% O₂, 350mg tobacco and heating rate of 120 K/min. As can be seen by comparingFIG. 14 and FIG. 15, the presence of Fe₂O₃ nanoparticles increases theratio of carbon dioxide to carbon monoxide present, and decreases theamount of carbon monoxide present.

Experiments were carried out in a quartz flow tube to study the effectof the iron oxide nanoparticles on reduction of carbon monoxide andisoprene in separate and combined gas flows. The concentration of carbonmonoxide, carbon dioxide and oxygen was measured by an NGA MLT 2000multi-gas analyzer. The concentration range of isoprene (not shown) wasmeasured by a Balzer Quadropole Mass Spectrometer (QMS). In theexperiments, 50 mg of iron oxide nanoparticles were used and the totalinlet gas flow rate was 1000 ml/min. During the experiments, the heatingrate was 12° C./minute. FIG. 16 shows the concentration of CO (curve A),CO₂ (curve B) and O₂ (curve C) and establishes that in the absence ofisoprene in the gas flow, the conversion of carbon monoxide to carbondioxide reached 100% at about 350° C. In the absence of carbon monoxidein the gas stream, the complete oxidation of isoprene took place atabout 375° C. as shown in FIG. 17 which shows the concentration of CO₂(curve A) and O₂ (curve B) and also shows the presence of a short burstof oxidation at about 240° C. The addition of isoprene (6000 ppm) to thecarbon monoxide containing gas stream promotes the carbon monoxideoxidation as shown in FIG. 18 which shows the concentration of O₂ (curveA), CO (curve B) and CO₂ (curve C) Essentially 100% conversion of carbonmonoxide was observed at about 225° C. and the isoprene was completelyoxidized to carbon dioxide and water at the same time as evidenced bythe extra carbon dioxide production and the extra oxygen consumption. Itwas further confirmed by QMS observation of the abrupt decrease of theintensity of m/e=68 (isoprene) to 0 and the increase of intensities ofm/e=18 (H₂O) and m/e=44 (CO₂). The analysis of the gas concentrationchanges in FIG. 18 confirms the following reactions occurredsimultaneously:CO+½O₂→CO₂C₅H₈+7O₂→5CO₂+4H₂O

In view of the data shown in FIGS. 16-18, it is believed that on thesurface of nanoparticle iron oxide isoprene actually promotes theoxidation of carbon monoxide instead of suppressing it and that carbonmonoxide also promotes the oxidation of isoprene. A similar effect wasnot observed for the oxidation of carbon monoxide and propene which hasonly one C=C double bond. Thus, it is theorized that some kind ofconcerted effect between carbon monoxide and the conjugated double bondcontaining compounds occurs in the presence of the nanoparticle ironoxide. A possible explanation is that the formation of acyclopentadienyl-like structure between the carbon monoxide and theconjugated double bond on top of the iron atom of the iron oxidenanoparticle. A cyclopentadienyl-like structure and (Cp)₂Fe is shown inFIG. 19. Nanoparticle iron oxide, with the higher population of thecoordinate-unsaturated iron site due to its small particle size, mightbe able to facilitate this surface complex and keep both carbon monoxideand isoprene close to the surface. It is expected that other types ofconjugated double bond containing compounds such as acrolein wouldundergo the same reaction.

The nanoparticle catalyst can effect reduction of various constituentsin mainstream and sidestream tobacco. Examples of constituents inmainstream that may be removed include, but are not limited to,aldehydes, carbon monoxide, 1,3-butadiene, isoprene, acrolein,acrylonitrile, hydrogen cyanide, o-toluidine, 2-naphtylamine, nitrogenoxide, benzene, N-nitrosonornicotine, phenol, catechol,benz(a)anthracene, and/or benzo(a)pyrene. With respect to isoprene, Withrespect to isoprene, in tests of three cigarettes containing 24 mg ofNANOCAT® in the tobacco rod, the average isoprene content in mainstreamsmoke was reduced to 286.3 μg compared to 413.6 μg for controlcigarettes tested in the FTC condition.

It is known that substituted phenols are present in cigarette smoke. Inorder to study the effect of nanoparticle catalysts on reduction of suchsubstituted phenols, catechol (C₆H₄(OH₂)) was selected as a phenolicmodel compound. The gas phase cracking of catechol over nano-particleiron oxide was studied in a flow tube reactor set up for catalyticcracking using a molecular beam mass spectrometer for realtime samplingfrom the reaction system and factor analysis to deconvolute complexchemistry. The effects of catechol/iron oxide ratio and temperature oncatalytic activity and cracking product distribution were studied inpartial oxidation conditions, i.e., 3% oxygen in an inert atmosphere.

The cracking study was carried out under atmospheric pressure in thetemperature range from 350 to 650° C. with about 10 milli secondscontact time. The ratio in weight % of substrate to catalyst was variedfrom 1:1 to 10:1.

Catechol (m/e=110) is thermally stable and requires high temperature(i.e., above 500° C.) to begin decomposing. However, significantcracking of catechol was observed even at 350° C. in the presence of thenanoparticle catalyst. Catechol underwent extensive conversion for the1:1 substrate/catalyst ratio at 350° C. over nano-particle iron oxide.The product distribution in the catalytic cracking of catechol at theseconditions is given in FIG. 20 where dominant products are found atm/e=44 (carbon dioxide) and m/e=28 (carbon monoxide) which could bepartially derived from carbon dioxide fragmentation in the ionizationprocess. This can be compared with the product spectrum resulting fromthermo-chemical conversion of catechol at 600° C. (FIG. 21) wherecatechol decomposed to the same extent as that observed over thecatalyst at 350° C. It is apparent from the figures that thermalconversion of catechol in the absence of the catalyst promoted theformation of compounds with the aromatic ring intact such as styrene(m/e=104) and indanone (m/e=132) by secondary reactions. The growth ofmolecular weight to form polycyclic aromatic compounds in the pyrolysisof catechol has been previously observed. These results indicate thatusing nanoparticle iron oxide in thermo-chemical conversion processesenhances complete cracking of phenolic compounds such as catechol togenerate neutral products such as carbon dioxide and water.

For the 10:1 substrate/catalyst ratio at 350° C., the decomposition ofcatechol was suppressed by the formation of higher molecular weightcompounds such as m/e=132 as shown in FIG. 22. At higher temperatures,the formation of compounds with an aromatic ring was promoted at theexpense of catechol. Comparable conversion of catechol for the 10:1 and1:1 ratios was observed at 650° C. (FIG. 23) and 350° C. (FIG. 20),respectively, while product distribution was completely different. Thiscan be attributed to secondary reactions at higher temperatures andcatechol concentration. Catechol conversion and product distributionover nano-particle iron oxide were dependent on sample/catalyst ratioand temperature. Therefore, having optimum process parameters can alterreaction products.

The nanoparticle additives, as described above, may be provided alongthe length of a tobacco rod by distributing the additive nanoparticleson the tobacco or incorporating them into the cut filler tobacco usingany suitable method. The nanoparticles may be provided in the form of apowder or in a solution in the form of a dispersion. In a preferredmethod, nanoparticle additives in the form of a dry powder are dusted onthe cut filler tobacco. The nanoparticle additives may also be presentin the form of a solution and sprayed on the cut filler tobacco.Alternatively; the tobacco may be coated with a solution containing thenanoparticle additives. The nanoparticle additive may also be added tothe cut filler tobacco stock supplied to the cigarette making machine oradded to a tobacco rod prior to wrapping cigarette paper around thecigarette rod.

The nanoparticle additives will preferably be distributed throughout thetobacco rod portion of a cigarette and optionally the cigarette filter.By providing the nanoparticle additives throughout the entire tobaccorod, it is possible to reduce the amount of carbon monoxide throughoutthe cigarette, and particularly at both the combustion region and in thepyrolysis zone. Further, the nanoparticle additive can reduce otherconstituents of mainstream and/or sidestream tobacco smoke, suchconstituents including aldehydes such as acetaldehyde or acrolein,hydrocarbons such as isoprene and phenolic compounds such as catechol.

The amount of the nanoparticle additive should be selected such that theamount of carbon monoxide in mainstream smoke is reduced during smokingof a cigarette. Preferably, the amount of the nanoparticle additive willbe from about a few milligrams, for example, 5 mg/cigarette, to about100 mg/cigarette. More preferably, the amount of nanoparticle additivewill be from about 40 mg/cigarette to about 50 mg/cigarette.

One embodiment of the invention relates to a cut filler compositioncomprising tobacco and at least one additive, as described above, whichis capable of acting as an oxidant for the conversion of carbon monoxideto carbon dioxide and/or as a catalyst for the conversion of carbonmonoxide to carbon dioxide, where the additive is in the form ofnanoparticles. Further, the nanoparticle additive can reduce otherconstituents of mainstream and/or sidestream tobacco smoke, suchconstituents including aldehydes such as acetaldehyde or acrolein,hydrocarbons such as isoprene and phenolic compounds such as catechol.

Any suitable tobacco mixture may be used for the cut filler. Examples ofsuitable types of tobacco materials include flue-cured, Burley, Marylandor Oriental tobaccos, the rare or specialty tobaccos, and blendsthereof. The tobacco material can be provided in the form of tobaccolamina; processed tobacco materials such as volume expanded or puffedtobacco, processed tobacco stems such as cut-rolled or cut-puffed stems,reconstituted tobacco materials; or blends thereof. The invention mayalso be practiced with tobacco substitutes.

In cigarette manufacture, the tobacco is normally employed in the formof cut filler, i.e. in the form of shreds or strands cut into widthsranging from about 1/10 inch to about 1/20 inch or even 1/40 inch. Thelengths of the strands range from between about 0.25 inches to about 3.0inches. The cigarettes may further comprise one or more flavorants orother additives (e.g. burn additives, combustion modifying agents,coloring agents, binders, etc.) known in the art.

Another embodiment of the invention relates to a cigarette comprising atobacco rod, wherein the tobacco rod comprises cut filler having atleast one additive, as described above, which is capable of acting as anoxidant for the conversion of carbon monoxide to carbon dioxide and/oras a catalyst for the conversion of carbon monoxide to carbon dioxide,wherein the additive is in the form of nanoparticles. A furtherembodiment of the invention relates to a method of making a cigarette,comprising (i) adding an additive to a cut filler, wherein the additive,as described above, which is capable of acting as an oxidant for theconversion of carbon monoxide to carbon dioxide and/or as a catalyst forthe conversion of carbon monoxide to carbon dioxide, wherein theadditive is in the form of nanoparticles; (ii) providing the cut fillercomprising the additive to a cigarette making machine to form a tobaccorod; and (iii) placing a paper wrapper around the tobacco rod to formthe cigarette. Further, the nanoparticle additive can reduce otherconstituents of mainstream and/or sidestream tobacco smoke, suchconstituents including aldehydes such as acetaldehyde or acrolein,hydrocarbons such as isoprene and phenolic compounds such as catechol.

In a test wherein a mixture of 0.74 g of tobacco filler containing 80 mgof catalyst material comprised of NANOCAT™ supported on 2-3 μm Al₂O₃(i.e., 30% NANOCAT™ and 70% Al₂O₃) was combusted and analyzed fordetermining reduction in constituents compared to control sampleswithout the catalyst, the results set forth in Tables 3a-d were observedwherein RTD is resistance to draw in units of mm H₂O and PC is the puffcount. TABLE 3a Vent Sample RTD % PC TPM (mg) CO₂ (mg) CO (mg) NO μg C185 21 8 18.5 39.82 15.75 264.9 C2 103 14 8.2 16.9 37.17 15.02 244.5 C3101 11 8 17.5 37.79 13.26 274.7 Avg. 96.3 15.3 8.1 17.6 38.3 14.7 261.4

TABLE 3b HCN CH₃CHO Isoprene MeOH COS C₂H₆ CH₄ Sample μg μg μg μg μg μgμg C1 144.3 656.4 413.7 102.1 37.52 56.39 508 C2 125.2 625.7 411.7 83.836.83 58.8 507 C3 130.9 723.7 415.4 115.3 33.1 55.55 498.1 Avg. 133.5668.6 413.6 100.4 35.8 56.9 504.4

TABLE 3c Vent Sample RTD % PC TPM (mg) CO₂ (μg) CO (mg) NO μg E1 121 137 8 31.64 9.26 195.6 E2 113 14 7.1 7 29.55 7.57 167.4 E3 128 13 7.7 8.933.62 9.25 198.4 Avg. 120.7 13.3 7.3 8.0 31.5 8.7 187.1

TABLE 3d HCN CH₃CHO Isoprene MeOH COS C₂H₆ CH₄ Sample μg μg μg μg μg μgμg E1 75.41 505.7 314 54.58 20.98 44.96 371.9 E2 60.29 458.3 247.7 54.5218.28 44.42 358.6 E3 72.63 518.8 297.1 69.86 21.66 48.24 415.5 Avg. 69.4494.3 286.3 59.6 20.3 45.9 382

Techniques for cigarette manufacture are known in the art. Anyconventional or modified cigarette making technique may be used toincorporate the nanoparticle additives. The resulting cigarettes can bemanufactured to any known specifications using standard or modifiedcigarette making techniques and equipment. Typically, the cut fillercomposition of the invention is optionally combined with other cigaretteadditives, and provided to a cigarette making machine to produce atobacco rod, which is then wrapped in cigarette paper, and optionallytipped with filters.

The cigarettes of the invention may range from about 50 mm to about 120mm in length. Generally, a regular cigarette is about 70 mm long, a“King Size” is about 85 mm long, a “Super King Size” is about 100 mmlong, and a “Long” is usually about 120 mm in length. The circumferenceis from about 15 mm to about 30 mm in circumference, and preferablyaround 25 mm. The packing density is typically between the range ofabout 100 mg/cm³ to about 300 mg/cm³, and preferably 150 mg/cm³ to about275 mg/cm³.

Yet another embodiment of the invention relates to a method of smokingthe cigarette described above, which involves lighting the cigarette toform smoke and drawing the smoke through the cigarette, wherein duringthe smoking of the cigarette, the additive acts as an oxidant for theconversion of carbon monoxide to carbon dioxide and/or as a catalyst forthe conversion of carbon monoxide to carbon dioxide. Further, thenanoparticle additive can reduce other constituents of mainstream and/orsidestream tobacco smoke, such constituents including aldehydes such asacetaldehyde or acrolein, hydrocarbons such as isoprene and phenoliccompounds such as catechol. “Smoking” of a cigarette means the heatingor combustion of the cigarette to form smoke, which can be inhaled.Generally, smoking of a cigarette involves lighting one end of thecigarette and inhaling the cigarette smoke through the mouth end of thecigarette, while the tobacco contained therein undergoes a combustionreaction. However, the cigarette may also be smoked by other means. Forexample, the cigarette may be smoked by heating the cigarette and/orheating using electrical heater means, as described in commonly-assignedU.S. Pat. Nos. 6,053,176; 5,934,289; 5,591,368 or 5,322,075, forexample.

While the invention has been described with reference to preferredembodiments, it is to be understood that variations and modificationsmay be resorted to as will be apparent to those skilled in the art. Suchvariations and modifications are to be considered within the purview andscope of the invention as defined by the claims appended hereto.

All of the above-mentioned references are herein incorporated byreference in their entirety to the same extent as if each individualreference was specifically and individually indicated to be incorporatedherein by reference in its entirety.

1-26. (canceled)
 27. A method of treating mainstream tobacco smokecomprising: lighting a cigarette comprising a cut filler composition andat least one nanosized catalyst to form smoke and drawing mainstreamsmoke through the cigarette, wherein the at least one nanosized catalystis capable of (a) converting isoprene and/or catechol to carbon dioxideand water vapor, and (b) conversing at least one aldehyde, hydrocarbonand/or phenolic compound to carbon dioxide and water vapor.
 28. Themethod of claim 27, wherein the at least one nanosized catalyst alsoreduces at least one additional tobacco smoke constituent comprisingnitrogen oxide.
 29. The method of claim 27, wherein the at least onenanosized catalyst also reduces at least one additional tobacco smokeconstituent selected from the group consisting of 2-naphtylamine,phenol, and mixtures thereof.
 30. The method of claim 27, wherein the atleast one nanosized catalyst also reduces at least one additionaltobacco smoke constituent selected from the group consisting ofacrolein, acrylonitrile, hydrogen cyanide, N-nitrosonornicotine,benz(a)anthracene, benzo(a)pyrene, and mixtures thereof.